All of UTA's TRAX and FrontRunner trains and stations, streetcars and streetcar stops, and all fixed route buses are compliant with Americans with Disabilities Act (ADA) and are therefore accessible to those with disabilities.[25] Signage at the stations, on the passenger platforms, and on the trains and streetcars clearly indicate accessibility options. Ramps on the passenger platform and assistance from the train operator may be necessary for wheelchair boarding on Blue Line trains. These ramps are not used on the Red or Green lines. In accordance with the Utah Clean Air Act and UTA ordinance, "smoking is prohibited on UTA vehicles as well as UTA bus stops, TRAX stations, and FrontRunner stations".[26]

TRAX operates seven days a week, with the exception of some holidays. It operates Monday through Friday from approximately 4:30 am to 11:30 pm with a fifteen-minute headway on each line during the entirety of operating hours. It operates Weekends from approximately 5:00 am to nearly midnight with a twenty-minute headway.[27]

The first line, running from downtown Salt Lake City south to Sandy, was completed in 1999. The second line from downtown to the University of Utah was completed in 2001 and extended in 2003. An extension to the Salt Lake City Intermodal Hub was completed in April 2008. In August 2011, two extensions to South Jordan and West Valley City were completed.[28] With the opening of these two extensions in 2011, the TRAX lines were renamed as colors instead of destinations, with the Blue Line running from the Salt Lake City Intermodal Hub to Sandy, the Red Line running from the University of Utah Medical Center to the Daybreak community in South Jordan, and the Green Line running from the intermodal hub to the West Valley Intermodal Hub. In 2013 the Green Line was realigned slightly north and away from the Salt Lake City Intermodal Hub, allowing for the opening of the extension to the Salt Lake City International Airport. Several months later, in August 2013, the Blue Line was extended further south to Draper (which opened August 18, 2013).[29] The extensions to South Jordan, West Valley City, Draper, and the Airport were funded in part by a Salt Lake County sales tax increase that would pay for all four of the proposed TRAX extensions.[30] A letter of intent signed with the Federal Transit Administration on September 24, 2007 secured the remaining funding for the light rail lines.[31]

Both the University Line and its extension to the University Medical Center were completed ahead of schedule. A daily ridership of 15,000 was expected for the initial 15-mile (24 km) line in 1999. By the beginning of 2008, the expanded system of 17.5 miles (28.2 km) served an estimated 40,000 passengers each day.[32] Ridership for the fourth quarter of 2012 was reported to be at 60,600, making it the ninth-busiest light rail system in the country.[20]

Light rail in the Salt Lake Valley was first seriously discussed in the late 1980s to provide an alternative to traffic congestion on I-15, but the idea was met with much criticism. On October 10, 1988, Congress approved $5 million in funds to preserve land along the proposed light rail corridor.[33] Funding for the light rail line itself, however, remained uncertain. After Salt Lake City won the bid for the 2002 Winter Olympics in 1995, UTA used the city's host status to accelerate obtaining funding through the Federal Transit Administration (FTA). Construction began in 1997. Protesters at the groundbreaking insisted that light rail would be both dangerous and a waste of money. Public opinion remained divided and businesses on Main Street in downtown Salt Lake City suffered during the construction period.

After the north-south line opened in late 1999 with sixteen stations, ridership expectations were quickly met. The system was enthusiastically embraced by valley residents, to the surprise of many, and once-skeptical communities soon began clamoring for extensions.

Funding for the University Line to Rice-Eccles Stadium allowed it to be completed in 2001 with four new stations, ahead of schedule and the Olympics. An extension to the University Medical Center that added three new stations was completed on September 29, 2003, fifteen months ahead of schedule.[34] An infill station at 900 South in Salt Lake City was constructed in 2005, and a second infill station, at 9400 South in Sandy (Sandy Expo), opened in August 2006. On December 13, 2006, the UTA Board of Trustees voted to change the name of the station next to the Delta Center to "Arena" in response to the renaming of the nearby indoor arena to EnergySolutions Arena.[35]

On February 23, 2006, plans for extending the main line westward to the current Salt Lake City Intermodal Hub near the Gateway District were approved. Two stations were built near the Gateway shopping district, as well as one at the Salt Lake Central Station (Salt Lake Intermodal Hub). They opened in April 2008,[36] bringing the total number of stations to 28.

UTA has two service centers for TRAX maintenance: the Lovendahl Rail Service Center, which is just off the Red Line in Midvale, southwest of its junction with the Blue Line, and the Jordan River Service Center, which is just off the Green Line northeast of River Trail. The Salt Lake City Southern Railroad, a subsidiary of the Utah Railroad, operates freight service over TRAX tracks via trackage rights.

On September 21, 2006, a property tax hike proposal was replaced with a general transportation quarter-cent sales tax hike that was voted on and approved on November 7 of that year. On December 21, 2006, the Salt Lake County Council created a priority list for the sales tax, saying that TRAX and commuter rail should take priority.[37] A letter of intent signed with the Federal Transit Administration on September 24, 2007 secured the remaining $500 million in funding for the light rail lines.[31] These funds were used to finance the FrontLines 2015 expansion project, which added four TRAX extensions by 2015 (as well as an expansion to FrontRunnercommuter rail).

In 2008, construction began on two new extensions: one extension of 5.1 miles (8.2 km) through West Valley City (now part of the Green Line) and another extension of 10.6 miles (17.1 km) through the southwest portion of the Salt Lake Valley (now part of the Red Line).[6] Both extensions were debuted in ceremonial openings on August 2, 2011,[28] and permanently opened for regular service on August 7. Both extensions were completed ahead of schedule and under budget.[28] Upon completion of these expansions UTA adopted a color-code line names in place of their old destination-based line names.

After the first year of operation, ridership on these portions of the Green and Red lines was less than was projected by UTA. However, UTA has stated that the projected ridership was for the year 2015. Since these lines were opened for service years earlier than originally planned, the anticipated growth on the west side of Salt Lake Valley has just not happened, yet. UTA affirms that by 2015 ridership will meet the original projections.[38]

A line from Salt Lake City International Airport to the University of Utah was in the original plans for the system to be completed before the 2002 Winter Olympics, but funding shortages only allowed for the eastern portion to be constructed. The airport line did eventually come to fruition, however, and ground was broken on October 22, 2008.[39] The extension opened on April 14, 2013,[40] adding 6 miles (9.7 km)[6] and six additional stations to the Green Line, including a transfer station to the FrontRunner.

On November 14, 2006, the Draper City Council approved the TRAX extension into that city.[41] Neighbors in the area have continually fought the route suggested by UTA. The route follows an old rail line and UTA already owned the right of way. An alternative route that would run down the middle of State Street was also studied by UTA.[42] Use of the UTA right of way for the line was challenged in court and was later approved by the Utah Supreme Court on July 12, 2008.[43] UTA published a draft Environmental Impact Statement for the new line that names the UTA right of way as the preferred route. Construction on the first phase of the extension, which includes 3.5 miles (5.6 km) and three new stations, has been completed and opened on August 18, 2013.[44] A second phase will eventually extend the line further south to 14600 South (near I-15, Exit 288), but dates have yet to be announced regarding the constructions and completion of this further extension.

When the FrontRunner (UTA's commuter rail train) started running on April 26, 2006, the only transfer station between the FrontRunner and TRAX was Salt Lake Central (Salt Lake Intermodal Hub), with the FrontRunner running north from that station to Ogden. However, with the opening of the FrontRunner South extension on December 10, 2012,[45] with service south to Provo, Murray Central was added as second transfer station. Although not part of the FrontRunner South extension, FrontRunner service at the new North Temple Bridge/Guadalupe station also began on the same day. When the Airport extension of the Green Line opened for service on April 14, 2013, this station became the third transfer station between FrontRunner and TRAX. The FrontRunner portion of this station was specifically built to provide a transfer station between FrontRunner and the Green Line, since the reroute of the Green Line for the Airport extension would have otherwise left the Green Line without any common station with FrontRunner.

For several years a TRAX spur into the Salt Lake City neighborhood of Sugar House had been contemplated. A series of community meetings were held in Sugar House as part of a larger transit study undertaken by UTA. Several transit alternatives were presented to the neighborhood, including bus rapid transit, light rail, and a streetcar.[46] The streetcar seemed to be the preferred alternative.[47] On October 20, 2010, the S Line (known then as Sugar House Streetcar) received a $26 million federal grant that allowed the street car to be completed in less than two years.[48] It used an existing rail line running along 2200 South from the Central Pointe TRAX Station to approximately 1100 East, near the primary Sugar House shopping district. The first phase of the S Line opened for service December 8, 2013.[49][50]

UTA has ordered a Draft Environment Study Report for transit alternatives in southern Davis County, including more comprehensive bus service, streetcar lines, and a TRAX line.[51] Some residents opposed UTA's proposal to bring light rail to southern Davis County.[52] In conjunction with the Mountain View Corridor project, there are also plans to eventually build a TRAX line on the west side of the Salt Lake Valley along 5600 West (in the same general area as the Mountain View Corridor).[53] The western line is anticipated to eventually replace the yet to be built 5600 West MAXbus rapid transit (BRT) line.

Following the completion of the FrontLines 2015 project, UTA has stated that they intend to focus on lower-cost projects such as streetcars and bus rapid transit. However, they do intend to eventually extend main TRAX lines as well. In addition to the aforementioned expansions, they also plan to extend the Blue Line from Draper to Lehi and eventually Orem. They are also exploring the possibility of mass transit to the ski resorts and possibly even to Park City.[54]

On January 25, 2014, UTA announced it had won a federal grant with the intention of establishing a new TRAX line that would directly connect the Salt Lake International Airport with the University of Utah. The former University Line originally ran along much of this route, but was replaced by the Red and Green Lines when the Mid-Jordan and West Valley extensions were completed in 2011. The west and east sides of Salt Lake City thus have no access to each other via TRAX without a transfer. The new line would use existing rail and trains, but more funding is required for software development, minor signal adjustments, and operator training. UTA is currently seeking these funds, but has no estimate for when the new line could begin operation. The new line would not only provide a direct east-west connection, it would also increase the frequency of TRAX service to downtown stations. UTA has yet to announce the name (color) of the new line. However, it has indicated that the new line will probably not connect all the way to the University Medical Center station, but may stop at the Stadium station instead.[55]

Unlike many other mass transit agencies,[who?] UTA does not sell naming rights for its stations, nor does it allow stations to be named after commercial businesses. Furthermore, commercial advertising on TRAX platforms is prohibited, in order for the passengers to be able to notice the safety information.[56] One exception to this rule occurred during the 2002 Winter Olympics. Since, for security reasons, the Arena and Temple Square stations were closed, UTA allowed Coca-Cola to use the area of the unused Arena Station as part of its pin-trading center.[57] The advertising restriction does not apply to the sides of the TRAX train cars or to UTA's buses. Not only does UTA have advertising signs on the sides and rear of many of its buses, it also has many buses where the painting scheme of the full rear or even the entire bus is an advertisement (bus wrap).[58]